The invention relates to a magnetic head, particularly for reading information from a magnetic registration medium, which magnetic head comprises a magnetic yoke having two limbs spaced at a distance from each other whose free ends constitute pole faces on either side of a read gap present between the limbs. The magnetic head also comprising a magnetoresistive element present within the magnetic yoke at a distance from the pole faces.
A magnetic head of the type described in the opening paragraph is known from U.S. Pat. No. 4,150,480, hereby incorporated by reference. The operation of such a magnetic head is based on the use of a strip shaped element of a ferro magnetic metallic material provided on a non-magnetic substrate, which element is provided in the vicinity of a magnetic registration medium for reproducing its information contents. The magnetic field of the passing registration medium brings about changes in the magnetisation state of the element and modulates its electric resistance via the so-called magnetoresistive effect. This means that the output signal of a detection circuit, which is connected to the magnetoresistive element, is a function of the information stored in the registration medium.
Since the change of the electric resistance of the magnetoresistive element under the influence of an external magnetic field is quadratic, it is common practice to improve the operation of the magnetic head by linearizing the resistance-magnetic field characteristic upon reproduction of signals. This can be realized in the known magnetic head, by positioning the axis of easy magnetisation parallel to the longitudinal axis of the magnetoresistive element and by providing means in the form of equipotential strips of a satisfactorily conducting material. Such a method is known from the article "The Barberpole, a linear magnetoresistive head" in IEEE Transactions on Magnetics, September 1975, Vol. Mag. 11, No. 5, pages 1215-1217.
Although the relation between the change of resistance of the magnetoresistive element and the intensity of the signal field can be linearized in a first approximation, for example, by means of the above-mentioned bias method, a drawback of the practical use of the known magnetoresistive head is that the noise level is high. This so-called modulation noise, also referred to as Barkhausen noise, is the result of the occurrence of more than one magnetic domain in the magnetoresistive element so that staggered domain walls are produced. Magnetic heads of the above-mentioned known type are also often comparatively little sensitive to small magnetic fields.
The modulation noise occurring and the low sensitivity have of course a detrimental influence on the signal to noise ratio of the known magnetic head.